xfs: don't rely on extent indices in xfs_bmap_insert_extents

Rewrite xfs_bmap_insert_extents so that we don't rely on extent indices
except for iterating over them.  Not being able to iterate to the previous
extent or finding the extent that stop_fsb is in are sufficient exit
conditions, and we don't need to do any extent count games given that:

  a) we already flushed all delalloc extents past our start offset
     before doing the operation
  b) xfs_iext_count() includes delalloc extents anyway

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
index cdec39bfd676b4f4f9edffe208ddc558488f2117..e77a71cc2f3ffba5154a4b43a64637df476bf00c 100644 (file)
--- a/fs/xfs/libxfs/xfs_bmap.c
+++ b/fs/xfs/libxfs/xfs_bmap.c
@@ -5737,10 +5737,8 @@ xfs_bmap_insert_extents(
        struct xfs_mount        *mp = ip->i_mount;
        struct xfs_ifork        *ifp = XFS_IFORK_PTR(ip, whichfork);
        struct xfs_btree_cur    *cur = NULL;
-       struct xfs_bmbt_irec    got, next, s;
+       struct xfs_bmbt_irec    got, next;
        xfs_extnum_t            current_ext;
-       xfs_extnum_t            total_extents;
-       xfs_extnum_t            stop_extent;
        xfs_fileoff_t           new_startoff;
        int                     error = 0;
        int                     logflags = 0;
@@ -5771,37 +5769,14 @@ xfs_bmap_insert_extents(
                cur->bc_private.b.flags = 0;
        }
 
-       /*
-        * There may be delalloc extents in the data fork before the range we
-        * are collapsing out, so we cannot use the count of real extents here.
-        * Instead we have to calculate it from the incore fork.
-        */
-       total_extents = xfs_iext_count(ifp);
-       if (total_extents == 0) {
-               *done = true;
-               goto del_cursor;
-       }
-
-       /*
-        * In case of first right shift, we need to initialize next_fsb
-        */
        if (*next_fsb == NULLFSBLOCK) {
-               current_ext = total_extents - 1;
-               xfs_iext_get_extent(ifp, current_ext, &got);
-               if (stop_fsb > got.br_startoff) {
+               current_ext = xfs_iext_count(ifp) - 1;
+               if (!xfs_iext_get_extent(ifp, current_ext, &got) ||
+                   stop_fsb > got.br_startoff) {
                        *done = true;
                        goto del_cursor;
                }
-               *next_fsb = got.br_startoff;
        } else {
-               /*
-                * Look up the extent index for the fsb where we start shifting. We can
-                * henceforth iterate with current_ext as extent list changes are locked
-                * out via ilock.
-                *
-                * If next_fsb lies in a hole beyond which there are no extents we are
-                * done.
-                */
                if (!xfs_iext_lookup_extent(ip, ifp, *next_fsb, &current_ext,
                                &got)) {
                        *done = true;
@@ -5810,18 +5785,13 @@ xfs_bmap_insert_extents(
        }
        XFS_WANT_CORRUPTED_RETURN(mp, !isnullstartblock(got.br_startblock));
 
-       /* Lookup the extent index at which we have to stop */
-       xfs_iext_lookup_extent(ip, ifp, stop_fsb, &stop_extent, &s);
-       /* Make stop_extent exclusive of shift range */
-       stop_extent--;
-       if (current_ext <= stop_extent) {
+       if (stop_fsb >= got.br_startoff + got.br_blockcount) {
                error = -EIO;
                goto del_cursor;
        }
 
        new_startoff = got.br_startoff + offset_shift_fsb;
-       if (current_ext < total_extents - 1) {
-               xfs_iext_get_extent(ifp, current_ext + 1, &next);
+       if (xfs_iext_get_extent(ifp, current_ext + 1, &next)) {
                if (new_startoff + got.br_blockcount > next.br_startoff) {
                        error = -EINVAL;
                        goto del_cursor;
@@ -5841,11 +5811,12 @@ xfs_bmap_insert_extents(
                        cur, &logflags, dfops, new_startoff);
        if (error)
                goto del_cursor;
-       if (--current_ext == stop_extent) {
+
+       if (!xfs_iext_get_extent(ifp, --current_ext, &got) ||
+           stop_fsb >= got.br_startoff + got.br_blockcount) {
                *done = true;
                goto del_cursor;
        }
-       xfs_iext_get_extent(ifp, current_ext, &got);
 
        *next_fsb = got.br_startoff;
 del_cursor: